WordPressで、記事内の最初の画像を持ってくる

the_content_image.php

<?php 
function the_content_image( $size = 'thumbnail', $align = "" ) {
  global $post;
	$output = preg_match('/<img.+class=[\'"]([^\'"]+)[\'"].*>/i', $post->post_content, $matches);
	if( $output ) {
		$first = $matches;
		preg_match("/wp-image-([0-9]+)/", $first[1], $matches);
		$attr = "";
		if( $align ) {
			$attr = array( "class" => $align );
		}
		echo wp_get_attachment_image( $matches[1], $size , false , $attr);

	} else {
		//$output = preg_match('/<img.+src=[\'"]([^\'"]+)[\'"].*>/i', $post->post_content, $matches);
		//echo $matches[0];
	}

	return false;


}
?>